Backflow Testing


San Lorenzo Valley Water District is committed to insuring a safe, high quality reliable drinking water system. An important part of San Lorenzo Valley Water District’s water quality program is its backflow prevention program.

Backflow is the reverse flow of water and other liquids or substances into distribution pipes in the potable water supply. A cross-connection is any actual or potential physical connection between a public water system, and any source of non-potable liquid, solid or gas that could contaminate the potable water supply by backflow.

Backflow prevention devices or backflow preventers are installed to prevent backflow of contaminants into drinking water through cross-connections.


The California Department of Public Health and San Lorenzo Valley Water District’s Rules and Regulations require the installation of an approved backflow prevention device under the following but not limited to conditions:

  • Any commercial, industrial and institutional property
  • Anywhere there is an auxiliary water supply such as a well
  • Anywhere that toxic concentrations of dangerous materials such as insecticides, weed killers, etc., are handled under pressure
  • Anywhere that fertilizer, livestock medications or vaccines, etc., are introduced into the water system
  • Anywhere animals are cared for
  • Anywhere irrigation (other than domestic) or gray water systems are employed
  • Anywhere a pump is utilized
  • Anywhere medical facilities exist
  • Anywhere a sewage treatment plant is operated

SLVWD can require a backflow devices be installed and repaired, as the responsability of the customer. All costs for installation, testing, and maintenance are the responsibility of the customer. The California Department of Health Services requires backflow devices to be tested annually. Testing must be completed by an approved tester.